Lake ice climatology

1.

Freezing lakes and lake ice
(1) Introduction
(2) Growth and melting
(3) Supraglacial lakes
(4) Lake ice climatology

2. Lake ice season

H = min thickness
for stable ice,
10 cm (small lakes)–
50 cm (large lakes).
Ice thickness
Stable ice ( climatology)
H
--- stable ice --tF
t1
t2 t b
Unstable
periods
(fixed)

3. Warming climate  ?

Warming climate ?
• Will the lake freeze in future ?
• How much are freezing date and break-up
date affected ?
• How much is ice thickness affected ? And
ice quality?
• Ice cover stability ?
• Ice coverage ?

4. Ice phenology

• Freezing date
• Strongly connected to air
temperature (long-wave
radiation, turbulent fluxes)
• Connection depends on
lake depth
• Freezing after 0oC
downcrossing
• Air temperature falling
rate major factor
time
Breakup date
• Solar radiation driving force
– no long-term trend
• Ice and snow thickness –
weak positive trend
• Turnover day from negative
to positive heat balance key
factor
• Degree-days correlate with
net solar flux
Thickness ~ ✔ freezing-degree-days

5. Freezing and breakup

P
E
R
E
N
N
I
A
L
Breakup
Freezing
80
No ice
Extrapolated from Kirillin et al. (2012)

6. Lake ice time series

Ice phenology
-freezing date
-breakup date
How to define?
Ice cover properties
•Ice thickness – max
annual value
•Ice concentration (large
lakes)
Variability
- independent winters
- interannual variability
externally forced
Aperiodic time series
outcome
- weak intra-seasonal
connections

7. Lake Kallavesi, Finland 1830 – 2014

Breakup
Freezing
- Trend 10 days/100 years
- Aperiodic
- Variability 45 days
-Trend 10 days/100 years
-Aperiodic
-Variability 80 days
-Extrema far from mean

8.

Colder climate less variability
Kirillin et al. (2012)

9.

Kilpisjärvi trends 1952 – 2010 (Lei et al., 2012)
Freezing
date
Breakup
date

10.

11.

12. 1st order: climate change impact

• Freezing date
~ 5 day/°C
• Ice thickness
5–10 cm/°C
• Breakup date
~ n days after zero
upcrossing of heating

13. Lake Vanajavesi: model for climate change impact

+6°C
+1°C
-1°C
-6°C

14. Ice thickness cycle – albedo sensitivity, Prydz Bay

Yang et al.
(2016)
a = 0.5
a = 0.7
a = 0.6
a = 0.5
Polar ice does not melt fully but breaks due to internal
deterioration. Light transmissivity of ice also has an
important role.

15. Lake Ladoga: Finnish – Soviet – Russian data

1943 – 1992
Aircraft observations
-Approx. twice a month
-Plots of ice distribution’
1971 ->
-NOAA
and
MODIS
satellite images
-On average 19 images
/winter
1913 – 1937
Ice charts and reports

16. Ice concentration A

• A = relative area of ice in
the lake
• Freezing depth: t = F(h)
• Hypsographic curve = G(h)
Formally:
A(t) = G[F-1(t)/max(h)
Thus fall evolution of ice concentration is related on the hypsographic
curve. Also decrease of concentration depends on that as melting starts
From shallow parts. Wind and lake size add further modifications.

17.

Lake Ladoga 1913–

18.

19. Summary: warming (?) 

Summary: warming (?)
Freezing day delays
Max annual ice thickness likely decreases
Ice quality (congelation ice/snow ice) ?
Period of stable ice cover shortens
Transient open water periods in smaller
lakes than presently
• Ice breakup date likely earlier

20. … consequences to water body

• Shorter ice season
AND
• More sunlight
• More transient open water periods
• Improved oxygen level
• How winter ecology will be adapted?

21. Climate warming  Lake seasons

Climate warming Lake
seasons
Annual cycle:
qualitative changes
- Summer stratification
stronger
- Stable ice period
shorter

22. Lake ice and society: climate change impact

• Lake ecology (+/- ?)
• Traffic on-ice
• Recreation: sport, fishing
ice-water bathing
• Local weather changes
warmer surfaces
• Open areas may persist
moisture fluxes, frazil ice
• Snow is main question!
Jacob Grimmer: Winter (1500s)
If the climate changes, not only the length of ice season and the
thickness of ice change, but the quality of physics, ecology and practical
life will be different.